1. Field of Invention
The present invention relates generally to medical devices and, more particularly, to devices used for determining physiological parameters of a patient.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, caregivers, such as doctors and nurses, desire to discover ailments in a timely manner in order to better care for patients. The unfortunate passage of time prior to discovering an ailment may limit treatment options and, in some instances, may lead to irreversible damage. If an ailment is discovered early enough, however, a variety of remedial options and corrective actions may be initiated in order to treat the condition and prevent further damage to the health of the patient. Accordingly, healthcare professionals are continuously pursuing methods to expedite the diagnosis of a problem or to anticipate a potential problem in order to better serve their patients.
Skin wounds stem from a number of different causes and understanding the etiology of the wounds allows for appropriate treatment. Some major categories for skin wounds include pressure ulcers (a/k/a bed sores), skin tears, venous ulcers, arterial ulcers, diabetic skin ulcers, and melanoma. The localization of fluid in the dermis is a precursor in a variety of skin wounds but is often not detected until signs of edema and the breakdown of skin become visually apparent. At this point, the number of treatment options is limited and initiating treatment generally results in a very slow healing process or a worsening of the condition. Concomitantly, changes in protein content in some pathologies result in increased risk of the development and/or morbidity associated with skin wounds. Epidermal hyper-proliferation and/or dermal fibrosis result in changes in the distensibility of the collagen networks and, therefore, the water holding capability of the tissue. Early detection of skin edema could significantly improve diagnosis and treatment of these morbidities.
The various types of skin wounds can be differentiated by knowing the patient history, as well as if and where the fluid is localizing. As an example, pressure sores are often marked by the presence of hemosiderin deposits (a protein resulting from the breakdown of red blood cells) and fluid accumulation in all layers of the dermis. Venous ulcers have a dramatic increase in fluid primarily in the papillary dermis. Alternatively, skin tears exhibit little change and a net loss of water from the dermis
Commonly, pressure sores occur on individuals where pressure is applied due to patient lying down or sitting in a chair and occur most frequently on the back of the head, the shoulders and shoulder blades, the elbows, the tailbone and base of the buttocks, the hips, the knees and sides of legs, and the heel and bony parts of the feet. In severe cases, pressure sores may necessitate amputation. Bed sores, for example, are a type of pressure sore seen in patients who have remained in bed for prolonged periods. Several discrete steps have been observed to be associated with the development of bed sores. Fluid is initially forced away from pressure points and then returns to create an inflammatory response causing redness and pitting. The redness leaves and eventually the skin hardens. Finally, the skin splits and a bed sore is formed. Other types of skin wounds, such as diabetic ulcers and cancer, develop differently and may not exhibit the same characteristics.
Currently, physical examination by the clinician and patient history are primarily used in determining skin wound etiology. To date, however, little work has been done to determine the spectral changes in the skin during skin wound development. In some cases, ultrasound technology is used to determine intradermal echogenicity. However, use of ultrasound technology may have several disadvantages. For example, ultrasound technology may not be sensitive to minor or minute changes, as the ultrasound technology only indicates when macroscopic changes have occurred. Additionally, ultrasound technology is not specific, meaning it may have inter-patient variability.
In addition to the localization of fluid in the dermis, excessive accumulations of fluid can occur in a variety of body compartments. Such accumulations may occur due to injury, inflammation, or excessive fluid resuscitation. In general, these accumulations cause an increase in pressure within the compartment and cut off blood flow, potentially causing organ failure and necrosis. Treatment typically requires incisions to relieve pressure. For example, abdominal compartment syndrome causes organ ischemia and failure, and it is commonly treated by opening the abdomen. Additionally, extremity compartment syndrome may cause ischemia and gangrene, and it is commonly treated by fasciotomies.
The occurrence of extremity compartment syndrome depends primarily on the precipitating injuries. For major fractures with associated vascular injury, prevalence has been estimated at 15-30%. Chronic and acute exertional compartment syndromes are also known. Extremity compartment syndrome is diagnosed by pain, paresthesia, pressure, pallor, paralysis, and pulselessness, in descending order of frequency and includes conditions such as shin splints and gout.
The prevalence of intra-abdominal hypertension (tissue pressure greater than 12 mm of Hg) has been estimated at 2-33% in the critically ill, with about half developing abdominal compartment syndrome (greater than 20 mm of Hg). Diagnosis and treatment of abdominal compartment syndrome currently begins at an intra-abdominal pressure greater than 12 mm Hg (normal is less than 5 mm Hg). Intra-compartmental pressures less than 20 mm Hg are generally considered acceptable only if carefully monitored.